After the shunt capacitor bank installed in the substation is out of operation, it must have a discharge device to release the internal charge. For the capacitor bank that implements automatic control switching, it is even more required to release its charge within a specified time. A safe voltage. The discharge resistance inside shunt capacitors often has certain quality problems, and its performance cannot meet the requirements of automatic switching. Therefore, the installation of special discharge coils is a necessary technical safety measure for shunt capacitors in substations.